Solution-phase stabilization of a cyclocarbon by catenane formation

Cyclo[<i>N</i>]carbons, molecular rings consisting solely of <i>N</i> carbon atoms, have previously been studied in the gas phase and on surfaces at cryogenic temperatures, but they are generally considered too reactive to be studied under ambient laboratory conditions. In this study, we report the synthesis of a cyclo[48]carbon catenane, in which the C₄₈ ring is protected by being threaded through three other macrocycles. This cyclo[48]carbon [4]catenane is stable enough for spectroscopic characterization in solution at room temperature. Its mass spectrum displays the expected molecular ions; its ¹³C nuclear magnetic resonance spectrum gives a single resonance for all 48 sp¹ carbon atoms at 72.9 parts per million; and its Raman spectrum shows an intense peak at 1890 inverse centimeters, similar to linear polyynes.